1. Field of Invention
This invention generally relates to the storage and transport of integrated circuit packages and devices for such storage and transport.
2. Background of Invention
This invention will generally be discussed in relation to integrated circuit packages of the type known in the industry as pin grid array (PGA) and its derivatives such as flip chip pin grid array (FCPGA) but the invention is not restricted to these particular types of integrated circuit packages but also to other sorts of electronic chips which have a plurality of pins extending from a body.
Storage trays for such integrated circuit packages have been produced by injection moulding processes. Such trays have problems with cost, weight and manufacturing complexity. Cost is a factor due to the amount of material required for injection moulding and the cost of that material and the manufacturing time. Problems also exist with such trays with stacking particularly when the trays are empty. Owing to the relatively thick sections used with injection moulding it is difficult to obtain a reduced volume when stacking empty trays.
An alternative moulding method involves the use of thermoplastic sheet materials. Thermoplastic materials have a number of known advantages. However, thermoplastic storage trays are typically not suitable for use for integrated circuit package storage trays due to their flexibility. A very flexible tray creates numerous handling problems.
One such example of such prior art is disclosed in U.S. Pat. No. 5,400,904. This specification discloses an injection moulded tray to hold a plurality of integrated circuit chips but it has weight problems with the thickness of the sections necessary for injection moulding. The particular configuration of the tray also does not allow for moulding reduced volume when stacking empty trays.
It is the object of this present invention to provide a storage and transport tray for integrated circuit packages which are considerably lighter and cheaper to manufacture and also provide other advantages.
It is also advantageous to have a storage tray which will support integrated circuit packages in an upside down position so that the pins can be inspected and it is a further object to provide a storage tray which provides this facility without the requirement of significantly more material and preferably without creating handling problems.
A first embodiment of the invention is a tray assembly for storing a plurality of integrated circuit packages, the integrated circuit packages being of a type having a body and a plurality of downwardly depending peripheral pins, the tray being formed by drape or vacuum thermoforming, the tray assembly further including a frame joined to the periphery of the tray to provide rigidity to the tray assembly.
Preferably the frame is injection moulded and is preferably joined to the tray by hot staking. The frame may include indexing lugs. Preferably the tray has a substantially uniform wall thickness, an obverse side of the tray having a plurality of recesses with each recess having a base and a central pedestal to engage in use an underside portion of the integrated circuit package such that the downwardly depending peripheral pins do not touch the base and upstanding walls to engage sides of the integrated circuit package, access recesses in at least some of the walls such that an integrated circuit package when supported in the recess can be engaged for removal by gripping at its edges, each access recess extending below the level of the base whereby on a reverse side of the tray the access recesses provide projections defining a retention area for an integrated circuit package with its pins facing upwards.
Throughout this specification the term xe2x80x9cobversexe2x80x9d will be used for the normally upper or top side of a support tray and the term xe2x80x9creversexe2x80x9d will be used for the normally lower or under side of a support tray.
The advantage of having the integrated circuit packages able to be supported and retained on both the obverse and reverse sides is that a pair of trays with a layer of integrated circuit packages sandwiched between them can be turned over so that the top tray can be removed so that the layer of integrated circuit packages can be viewed and in particular the pins of the next layer of chips can be inspected for any blemishes.
A second embodiment of the invention is directed to the tray per se. This embodiment is a tray for storing a plurality of integrated circuit packages, the integrated circuit packages being of a type having a body and a plurality of downwardly depending peripheral pins, the tray being formed by drape or vacuum thermoforming whereby to have a substantially uniform wall thickness, an obverse side of the tray having a plurality of recesses with each recess having a base and a central pedestal to engage in use an underside portion of the integrated circuit package such that the downwardly depending peripheral pins do not touch the base and upstanding walls to engage sides of the integrated circuit package, access recesses in at least some of the walls such that an integrated circuit package when supported in the recess can be engaged for removal by gripping at its edges, each access recess extending below the level of the base whereby on a reverse side of the tray the access recesses provide projections defining a retention area for an integrated circuit package with its pins facing upwards.
In a preferred form of the invention the access recesses are provided in a middle portion of each wall and the wall portions are provided at each corner of the recess.
Each pedestal may include a central recess.
Preferably each storage tray has a plurality of locating pins in use adapted to engage with the underside of an adjacent tray to enable stacking of a number of trays. The locating pins may be at the corners of each trays.
There may be provided indexing engagement points on the sides or ends of the trays so that the tray can be accurately transported through a piece of insertion equipment so that robotic arms and the like can accurately pick the integrated circuits from the tray.
Each storage tray may have a plurality or rows and columns with a recess at the intersection of each row and column and in a preferred embodiment of the invention there may be two rows and five columns.
Preferably, at the intersection of each wall portion of a recess a cutaway is provided such that the corner of an integrated circuit package when supported in the recess does not engage with the tray thereby preventing jamming of the integrated circuit package into the tray.
Preferably each of the various walls and portions of the storage tray according to this invention are angled or tapered so that the storage trays when empty may be stacked in a reduced volume for transport.
It will be seen therefore that the invention provides a storage tray using a thermo-forming method which provides advantages such as lower mould cost, quicker mould manufacturing lead time, lighter tray weight, lower material costs, faster tray manufacturing cycle costs and lower transportation costs. Essentially the thermoforming technique uses a thermoplastic sheet material which is heated to a softening temperature and draped over a mould and assisted by vacuum or pressure to form into the shape of the mould after which it is cooled until the material takes the shape of the mould.
Furthermore these trays may be used as part of a rigid tray assemble as described in the first embodiment of the invention.
Such a storage tray assembly may use larger storage trays as the overall assemble will be more rigid. This assembly would be rigid within fixed tray dimensions in accordance with established JEDEC standards. For example the tray assemble could have three rows of eight recesses to hold 24 semiconductor chips.
An advantage of using the trays of the second embodiment within the tray assembly of the first embodiment is that the overall tray assembles gain most of the advantages of the tray, and the assembles are stackable when empty. However, it is envisioned that it will not be possible to stack the assembles in a reduced volume due to the rigid frame.
This generally describes the invention but to assist with understanding reference will now be made to the accompanying drawings which show preferred embodiment s of the invention.